Stacking machine



, H. HILL STACKING MACHINE June Q1942,

Filed Nov. 10, 1941 4 Sheets-Sheet l N 1 I /E/PMANN H /LL Y U ATTORNEY H. HILL STACKING MACHINE 'Filed NOV. 10, 1941 June 9, 1942.

4 Sheets-Sheet 2 ATTORNEY June 9, 1942. H. HILL 7 2,285,814

STACKING MACHINE Filed Nov. 10, 1941 i 4 Sheets-Sheet 5 fig INVENTOR HERMAN/v H/L L ATTORNE..

June 9, W420 H. HILL 2,285,814 I STACKING MACHINE Filed Nov. 10, 1941. 4 Sheets-Sheet 4 INVENTOR HERMANN /LL (14?, Y 1 I ATTORNEY Patented June 9, 1942 UNITED STATES i PATENT OFFICE Application November 10, .1941, Serial No.418,607

Claims.

The invention relates to machines for stack ing articles, more particularly articles that are thin, as, for example, razor blades and thelike.

The main object is a machine of that character capable of stacking the articles rapidly 'and ,5

accurately and without injury to them.

Another object is a stacking machine for especially thin articles, the-stacking mechanism of which is capable of very fineand accurate adjustment.

While the machine is adaptable as above stated for stacking a great variety of articles, I will, for purposes of illustration, describe it as adapted to stack razor blades preparatory for dispensing them to the consumer.

Referring to the drawings:

Fig, 1 is a plan view of the machine;

Fig. 2 is a plan view showing the blade strip feeding and breaking mechanisms;

Fig. 3 is a side elevation corresponding to Fi 2;

Fig. 4 is an end view corresponding to Fig. 3;

Fig. 5 is a side elevation showing the blade form;

Fig. 7 is an enlarged plan view of theblade stacking mechanism;

Fig. 8 is an end view corresponding to Fig. 7; Fig. 9 is a view on the line 9-9 of Fig. 7;

Figs. 11 and 12 show the two slides separated from each other which operate directly to build the stack;

Fig. 13 is a perspective View of the entrant end of the tray.

breaking mechanism and .the blade stacking mechanism,:are all-operated through appropriate gearing from the shaft l3.

Strip feeding mechanism Considering-the strip' feeding mechanism (best shown in Fig. 3),the shaft [3 'is provided with an eccentric III on which is rotatably mounted thebearing I5 of the "connecting rod '16. The

. opposite end of the connecting rod is provided with a bearing I1 rotatably mounted on an eccentric stub shaft f8 extending from socket l8a on the slide'block 2'0. The slide block is slidably mounted on the guide 2| and. is thereto packing them in cartons orother receptacles '15 fore capable OfaIGCiPrOCatiHg motion equal to twice the radius of eccentricity of the eccentric M. The guide .2] .is .fixedly mounted to the frame 22 which supports the operating parts.

The stub shaft 18 is secured in a socket 23 T20 fixedly mounted on the slide block. By loosenloading. platform and accompanying mechanism; 25 @h'anged- A150 there mounted on t e ide Fig. 6 is a plan view of the blade loading platblock a bell crank lever 24 mounted to rock on the stub shaft 25. One arm 26 of the bell crank lever is provided with a stopIZl in the form of a screw for micrometer adjustment .and a lock 30 nut '28 for locking the screw in any set position.

The otherarm .30 of the bell crank lever is provided with asmall stub shaft 3| on which is rockably mounted a pawl 32 spring-pressed by the spring 320. in a clockwise direction. The

spring'is stifi'enou'gh to cause feeding of the strip,'but weak enough to yield "if an obstructionto the feed 'is met. An adjusting screw '33 threaded into the block 34limits theramount of The blade strip which the machineisadapted m rotation "of which the pawl is capable under the to separate into single blades and to stack them T stacking mechanism, and the blade stacking platform.

influence of the spring, and the screw may be adjusted to any position within the range of its'efiec'tive' length. The'tension spring 35 conne'c't's the arm 26 of the bell crank lever with a pin 36 in the "slide block'ZD and draws the stop 21 yieldingly into abutment with the socket 233. 'The stroke of the slide block is adjusted to the spacing of the notches in the heel of the blade strip. The blade strip, as shown, is feeding in the direction of the arrow A (Fig. 3). As

the slide block is retracted when the eccentric I4 rotates to its rearward positioni, e., to the left as shown'inFig. 3, the spring 35 flexes and the pawl 32 trails. along the'he'el .oftheblade The strip feeding mechanism, as also the-'55 strip, and due to the. spacing of the'notches,

enters a notch at the end of its rearward stroke or it may overrun a notch slightly and pick it up on the feeding stroke. As the motion of the slide block is reversed, the pawl, having entered a notch, advances the strip the length of a single blade.

Since the action of the pawl would lift or tend to lift the blade strip were the latter not confined, there is provided a pair of rollers 40 and 4|, each having a peripheral groove 42 of insuflicient width to permit a blade to enter therein beyond its extreme cutting edge. The cutting edge of the strip is therefore not injured as it passes beneath the idler rollers and through the grooves in their peripheries. The idler rollers are mounted on a block 43 erected on the frame of the machine.

In order to prevent the blade strip from being retracted by the friction of the pawl 32 during the retractive movement of the slide block, a check pawl 46 rotatably mounted on the pin 46a projecting from the frame is provided. A spring 461) connecting the pawl with the block 460 tends to cause the pawl to rotate in a clockwise direction. As the blade strip travels in its feeding direction, this pawl trails along it exerting only as much pressure thereon as the spring is capable of exerting, which need be very little. However, any retrograde movement of the blade strip that might be caused by the rearward drag of the pawl 32 immediately causes a checking or snubbing action to take place.

Braking mechanism The purpose of this mechanism is to break the blades from the strip one by one as successive pairs of notches reach a designated position. This is done by means of the hammer head 60 (Figs. 2 and 3) bolted as shown to the arm 6| of a lever pivoted at 62 to the frame of the machine. The short arm 63 of the lever carries a cam following roller 64, which follows the periphery of the cam 35 as the latter fixedly mounted on the main shaft I 3 rotates. In the cam profile there is a rather abrupt inturn toward the shaft I3, as shown at 66, and as the cam rotates anti-clockwise as indicated by the arrow B (Fig. 2), the cam following'roller B4 is thrown suddenly toward the shaft I3 by the expansion of the spring 61, surrounding the rod 610. and 6 interposed between the head 61b and the stop 610. The rod is hingedly connected to the hammer lever at 68. The hammer therefore delivers a sharp blow against the blade strip, the notches of which are in line with the slit 68 in the anvil I0 and the blunt edge II of the hammer, it being understood that the feed is so timed as to cause the strip to dwell in the position just mentioned as the blow is struck. The blade strip being of verse line through opposing notches of a pair. The stroke of the hammer is so timed with respect to the stroke of the slide block 20 that Blade stacking mechanism The general relationship of the blade stacking mechanism to the remaining units is shown in hardened steel is therefore severed, or perhaps more correctly speaking fractured, on a trans- Fig. 1. The mechanism itself is shown in detail in Figs. 7-12, both inclusive. Its object is to stack the blades that have been severed from the blade strip by the hammer as will be later described. As successive blades are severed by the hammer, they travel in tandem, impelled by the feeding mechanism, in a groove 89 in the guide 8|. As the severed blades successively reach the stacking mechanism, the stack is, during the retractive movement of the feed slide 2|), forced upwardly at each stroke against gravity and friction a distance equal to the thickness of a blade. This is accomplished by means of two slides indicated generally by the letters K and L (Fig. 12) and the necessary operating and adjusting mechanism. The slide K comprises two rails 82 and 83 connected together by a plate 84, there being fixedly mounted on the rails two blocks 86 and 81 which bridge them. Also there is fixedly attached to the plate 84 a depending block 90. It may be considered as two slides rigidly connected together. The slide L comprises a narrow plate of a width to slidingly fit between the rails of the slide K, and it is provided with a fixedly attached depending block 9|.

The depending block 90 is smooth-bored at 92 to accommodate a plunger 93 and is counterbored to accommodate the extension spring 94, the head 95 of the plunger bearing against the spring. Adjustment of the plunger is desirable in order to vary its stroke as will appear, and for this purpose the nut 96 is provided into which the plunger is threaded. The nut is prevented from turning as the plunger is adjusted, by the stud 91, which enters the groove I00. The plunger is set to any given position by the set screw IIiI, which enters the annular groove "Win the plunger. As will presently appear, the adjustment is made use of to vary the width of the gap 95a.

In the block 81, which forms a part of the slide K, as has been described, is threaded a screw I05, which by abutting against the block I66 establishes a limit to the movement of the slide K in a right-hand direction as shown in Fig. 9. This limit can be varied by adjusting the screw, which is set to a fixed position by the set screw I61.

The stroke of the slide K is limited in a lefthand direction (Fig. 9) by the screw II I threaded into the stop block III] aflixed to the frame. This limit may obviously be varied by operating the screw which opposes the block 86 on the slide The slide L, as has been noted, operates between the rails 82 and 83 of the slide K. The block 8| is provided with a threaded bore which accommodates the screw II2, which is fixed in any set position by the set screw I I3. By turning this screw one way or the other, the width of the gap I93 may be varied. A limit to the right-hand movement of the slide L is established by the screw II4, which enters the block 9|. The screw has a loose fit in the frame portion H5 and is provided with a stop nut H6 and a lock nut III.

The slide K is spring-pressed forwardly (as shown in Fig. '7) by the lever I20 pivoted on the stud I2I projecting from the frame I22. The contractile spring I23 exerts apull on the long arm of the lever causing the end of the short arm to bear against the abutment I24 of the slide. The slide L is similarly actuated by the lever I25 and the contractile spring I26, the short arm of the lever bearing against the abutment I25a.

The slides are operated from the main shaft I3 through the cam I21, the cam follower I29, the lever I30 pivoted to the frame at I3I, the connecting rod I32 pivoted to the lever at I33, and to a bell crank lever I34 at I35. The bell crank lever rocks on a stud I36 projecting from the main frame and is pivotally connected at I31 to a second connecting rod I38. This connecting rod is, in turn, pivotally connected at I40 to a lever I II which rocks on a stud I42 projecting from the frame. The free arm I43 of this lever is provided with a stud I95. The track of the peripheral cam I21 has a high portion and a low portion, the high portion serving to operate the lever I4I to drive the plunger 93 to the left and the low portion serving to release the plunger and permit the levers I20 and I25 to operate the slides.

At this point the mode of operation of the blade stacking mechanism will be described, and to assist in the explanation reference is made to Figs. 10a, 10b, and 100, showing a cycle of steps in adding a blade to the bottom of the stack X.

The cycle may be assumed to begin when the parts are in the position shown in Fig. 10a i. e., when both slides impelled by their actuating springs are in the extreme forward position-i. e., toward the upper part of the sheet as shown in Fig. 7. In this position the bottom blade of the stack, and consequently the entire stack, is resting against the working faces of the slides, the bottom blade itself being offset from the line of travel of the feed a distance equal to a blade thickness. Next, the slide is retracted to clear the line of feed and the incoming blade I65 is thrust by the feeding mechanism behind the bottom blade of the stack until it is about halfway across the slide L, whereupon the slide L is retracted and the blade I95 continues until the feeding stroke is completed. The slide K is beveled off at I960; and I05b and the slide L is beveled off at I960 to allow unimpeded travel of the incoming blade. This completes a cycle, and of course it is repeated as each successive blade is added to the stack.

Having described the cycle of steps carried out by the stacking mechanism, the way in which it is carried out will now be described:

Referring to Fig, 9, a stud I54 has a fixed stroke, fixed not only as to length but as to position of its extremities. Forward motion 'of the slide K is limited to a desired position by adjusting the screw I05 so that it bears against the block I05 when the slide K is in the position shown in Fig. a. Rearward motion of the slide K is limited by the adjusting screw II I, which is adjusted to stop this rearward motion when the slide is in the position shown in Fig. 1022.

Forward motion of the slide L is limited by the stop nut II6 on the screw II5, which is threaded into the block SI. Rearward motion of the slide L is limited by the position of the screw H2, also threaded in the block 9I and set to a fixed position by the set' screw II3. When the working stroke of the lever I iI takes place, the stud I56 contacts with the head 95 of the plunger 93. The spring 95 is considerably stiffer than the springs I23 and I25 and is preferably preloaded, and therefore the slide L is driven rearwardly against the relatively Weak opposition of the springs I23 and I26. contacts with the adjusting screw I I I, rearward motion of the slide K ceases, but since there is a positive stop to this rearward motion, the

spring 94 is now compressed, and then the slide When the block 86 L is in turn carried back to the position shown in Fig. 100, its limit of rearward motion being fixed as-above stated by properly positioning the adjusting screw II2. Adjustment of the plunger 93, in order that it may have a proper relationship to the stroke of the lever MI is effected by turning it one way or the other as required in the nut 96, which is non-rotatable by virtue of the stud 91 entering the groove I00. The plunger may be set by means of the set screw I'0I.

It will be apparent that provision has been fully made for fixing notonly the length of stroke of both slides but also the forward and rearward limits for any given length of stroke. Since the absolute length of the stroke is in any case'very small, being not more than the thickness of a blade which may not be in excess of .010, it will be apparent that this very fine adjustment is necessary.

7 Blade stacking platform As each blade is moved laterally by the blade stacking mechanism, it passes into an inclined trough I driving ahead of it any blades which have previously been stacked. Thence it passes along with the preceding and succeeding blades into the tray I5I. The tray has side walls I52 and I53 for confining the stack, and the stack as a whole moves along skids I54, I54. The tray is provided with a gate I55 which is hinged on the rod I56, which in turn is mounted in the bearings I51 and I58. A torsion spring I59 exerts a force that normally keeps the gate raised, so that, in order to permit blades to enter the tray, the gate may be raised by releasing it from the spring catch I59a. When the gate is lowered, the spring catch I59a snaps into the notch I59b of the gate and holds it closed. The lower edge of the gate may be sharp so that it may, in lowering, enter easily between adjacent blades of the stack. The tray rests on an inclined platform I 50, and is located in a position laterally by means of two cradles I6I and I62 which are carried at the ends of arms I63 and I64. The cradles normally project above the surface of the platform but are capable of being pressed down until they are wholly below the surface of the platform. This is accomplished by rigidly mounting the arms on the shaft I65 which is supported in bearings I56 and I51. A torsion spring I10 is provided and this normally causes the cradles to project above the surface of the platform. They are, however, prevented from rising beyond a certain distance by the projections H011 and H01) which abut against the lower side of the platform.

It will be observed that the ends of the cradles slant downwardly toward the platform. The purpose of this will be presently explained.

In the ordinary'use of the machine it is highly desirable that, when a tray has been fully loaded, it be removed as quickly as possible and a new one substituted therefor in order that it shall not be necessary to stop the machine. I therefore provide a mechanism which in co-operation with the cradles effects this purpose. It comprises two arms I89 and I8I beneath the stacking platform but terminating in hooks I82 and I33, which project upwardly above the surface of the stacking platform through slots I04 and I85 in the latter. They are supported by pins I86 and I31 which can ride along the platform. The arms are pivotally connected at I and I9I to arms I92 and I93, these latter arms in turn being non-rotatably mounted. on the shaft 194.

The shaft I94 is supported by hangers I95 and I96 in which it may rotate. A handle I91 is non-rotatably mounted on the shaft I94. By rotating the handle clockwise as shown in Fig. 6, the hooks are drawn along the slots. An empty tray may be placed on the platform against the hooks. By rotating the shaft I94 clockwise (see Fig. 6), the empty tray is drawn laterally, forcing down the cradles and thus releasing the loaded tray until the empty tray is properly aligned with the trough, whereupon the cradles snap up and secure it in place, The loaded tray may then be removed. If desired, stops 200 and 2M may be provided to prevent overthrow of the loaded tray, and stop 292 may also be provided to resist any upward push as the tray is being filled.

Before the last described operation is carried out, the gate to the loaded tray is of course closed, the stack of blades being separated by a suitable tool to permit this to be done.

While I have described a certain particular construction in which my invention is incorporated, I do not desire to be limited to this particular embodiment since many changes and modifications may easily be made without departing from the spirit and scope of the invention as set forth in the following claims.

I claim:

1. In a machine for stacking razor blades and the like, a pair of independently movable slide units, stops adapted to limit the movement of each unit in both directions, sprin means normally urging both the slide units to advance position, one of the units being provided with additional spring mean more resistant to flexure than the spring means urging it to advance position, means acting intermittently on the said additional spring means to retract the said slide unit against the resistance of its advancing spring means and to effect engagement with the second slide unit and cause retractive movement thereof after the first-mentioned slide unit has been fully retracted, and means for feeding articles across the path of the slide units and in advance of their working faces.

2. In a machine for stacking razor blades and the like, a pair of independently movable slide units, one of the units comprising a pair of spaced connected slides and the second unit comprising a single slide positioned between the members of the pair, stops adapted to limit the movement of each unit in both directions, spring means normally urging both the units to advance position, the first-mentioned unit being provided with additional spring means more resistant to flexure than the spring mean that urges it to advance position, means acting intermittently on said additional spring means to retract the said first-mentioned slide unit against the resistance of its advancing spring means and to effect engagement with the second sli-de unit and cause retractive movement thereof after the first-mentioned slide unit has been fully retracted, and means for feeding articles across the path of the slide units andin advance of their working faces, the said working faces being chamfered to permit the feeding of such articles without positive obstruction thereto.

3. In a machine for stacking razor blades and the like, a pair of independently movable slide units, one of the units comprising a pair of spaced connected slides and the second unit comprising a single slide positioned between the members of the pair, stops adapted to limit the movement of each unit in both directions, spring means normally urging both the units to advance position, the first-mentioned unit being provided with additional spring means more resistant to flexure than the spring means that urges it to advance position, means acting intermittently on said additional spring means to retract the said first-mentioned slide unit against the resistance of its advancing spring means and to effect engagement with the second slide unit and cause retractive movement thereof after the first-mentioned slide unit has been fully retracted, and means for feeding articles across the path of the slide units and in advance of their working faces, the said working faces being chamfered to permit the feeding of such articles without positive obstruction thereto, the initial stage of the feed taking place as the first-mentioned slide is retracted and the said feed continuing into completion as the last-mentioned slide is retracted.

4. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for the third slide respectively normally urging the slides to advance position, a rear stop interposed in the path of the pair of slides for limiting their retractive movement, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked, means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance position impelled by their respective spring means.

5. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for 'the third slide respectively normally urging the slides to advance position, a rear stop interposed in the path of the pair of slides for limiting their retractive movements, a forward stop also interposed in the path of the pair of slides for limiting their advance movement, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked, means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop, and then position means.

to continue the travel of the plunger'against'the resistance of its spring and against "the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance impelled by their respective spring 6. In a machine for stacking razor blades-and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members'of'the pair, separate Spring means for the pair of slides and for the third slide respectively normally urging the slides to advance position, an adjustable rear stop interposed in the path of the pair of slides for limiting their re tractive movements, an adjustable forward stop also interposed in the path of the pair of slides for limiting their advance movement, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked, means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance position impelled by their respective spring means.

7. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for the third slide respectively normally urging the slides to advance position, stops interposed in the paths of travel of the slides adapted to limit both their advance and retractive movements, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked, means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop for the pair of slides, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance position impelled by their respective spring means. I

8. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for the third slide respectively normally urging the slides to advance'poadvance motion of the slides,'said spring being stiffer thanthe spring means acting on the pair of slides, an adjustable stop associated with the plunger opposing said'spring, an adjustable abutment on the third slide positioned in the gline-of travel-of the plunger and spacedtherefrom a distance at least equal to the thickness of the articles to be stacked, means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop for the pair of slides, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance position impelled by their respective spring means.

9. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for the third slide respectively normally urging the slides to advance position, a rear stop interposed in the path of the pair of slides for limiting their retractive movement, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked,

means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third slide is retracted, and then to release all the slides for travel to advance position impelled by their respective spring means, and means for feeding said articles one by one across the path of movement of the slides and in advance of their working faces, the initial stage of the feed taking place after the pair of slides is fully retracted and continuing to completion as the third slide is retracted.

10. In a machine for stacking razor blades and the like, a pair of connected spaced parallel slides, a third slide positioned intermediate the members of the pair, separate spring means for the pair of slides and for the third slide respectively normally urging the slides to advance position, a rear stop interposed in the path of the pair of slides for limiting their retractive movement, a plunger mounted on the pair of slides and parallel with them, a spring acting on the plunger and normally urging it in the direction of the advance motion of the slides, said spring being stiffer than the spring means acting on the pair of slides, an abutment on the third slide positioned in the line of travel of the plunger and spaced therefrom a distance at least equal to the thickness of the articles to be stacked, means adapted to operate intermittently on the plunger to cause the said pair of slides to retract against the resistance of the spring means acting upon them until arrested by the rear stop, and then to continue the travel of the plunger against the resistance of its spring and against the resistance of the spring means acting on the third slide until the said third 

